As technological advances continue at an ever increasing rate, the need for easier access to certain categories of data increases, including satellite navigational data and satellite location data for a business or an individual who needs to organize ground based activities that depend on data streams from a particular satellite. For a given location and time or range of time, specific information that may be needed in this context include which satellites are available or visible; which satellites provide optimal viewing azimuth, elevation and range; the ground swath for a given satellite; etc. The data from satellites also can be useful in ground truth operations, i.e., authentication of a ground position, or the use of a ground station that provides a reference point on Earth. Thus, transmission of data to, or receipt of data from, a particular satellite will be required for particular operations. Therefore, knowledge of the particular satellite's position for a given Earth location and time will facilitate the planning of operations dependent on that satellite. In addition, where any one of several satellites may be used for a given task, and one satellite is "overloaded", knowledge of alternate available satellites will facilitate completion of the operation. Similarly, where routing of signals between satellites is required for data transmission, alternate satellites may be used to provide bypass routes to compensate for an overloaded or malfunctioning satellite.
A variety of inventions have been developed that are portable, and -- due to their relatively small internal CPU's -- require periodic updating or other information transfer from a base unit with a larger CPU. Some of these inventions rely on satellite data to facilitate ground level operations. Other inventions have no satellite communication requirement, but do require updating of the limited data stored in a portable unit with modest internal memory. One such invention is that of U.S. Patent No. 5,682,525 to Bouve, et al., entitled "System And Methods For Remotely Accessing A Selected Group Of Items Of Interest From A Database", which discloses a means for remote access to positional/geographical, business, architectural, and other data. Satellite communications are utilized for navigational/location and other data. Optionally, advertisements for businesses in a selected area may be included in the output data stream.
U.S. Patent No. 5,659,741 to Eberhardt, entitled "Computer System And Method For Storing Medical Histories Using A Carrying Size Card",discloses a means to store a person's medical history on a credit card sized device, and access that information at a hospital, physician's office, ambulance, or other medical facility upon reading the information stored thereon. Thus, the comatose or unconscious patient's medical history can be accessed instantly, and thereby save time and possibly lives. The disclosed system and device can also be used for other purposes, for example, in monitoring the effects of a drug on a patient. By using the patient's credit card sized device, additional or updated information can be obtained and stored on the device by accessing the patient's file from a remotely located database.
U.S. Patent No. 5,652,570 to Lepkofker, entitled "Individual Location System", discloses a system for locating and continuously monitoring the location of a person, as well as medical or other information pertaining to that person. A wrist watch is worn by the person, and transmits information over radio frequency to the transponder of a pod unit that the person wears on a belt. - The pod unit transmits the received information to a central monitoring system. The central monitoring system can transmit alerts and inquiries to the pod unit, which in turn can transmit those alerts/inquiries to the wrist watch.
U.S. Patent No. 5,633,799 to Dussell, entitled "Combined PC/104 And Satellite Positioning System", discloses a portable apparatus for determining the location and time of observation of an individual. The apparatus can be a card or other portable device that conforms to the IEEE PC/104 Standard, and that includes a Satellite Positioning System (for example, GPS or GLONASS). An antenna to receive satellite signals (and frequency downconvert if necessary) is included, as are various microprocessors and buffers. The system is capable of performing calculations to determine position and time of observation, as well as formatting, display, signal processing, and other functions. An information transfer module is optionally included to permit information transfer to another electronic device.
U.S. Patent No. 5,627,548 to Woo, et al., entitled "Navigation Wristwear", discloses a wristwear device with a GPS receiver. A transparent microwave patch antenna is included, along with an LCD, and several elements on a single integrated circuit: a low-noise amplifier, a downconverter, a code processor, and a navigation processor. Two photovoltaic solar cells help maintain battery charge.
U.S. Patent No. 5,543,802 to Villevieille, et al., entitled "Position/Navigation Device And Method", discloses a means to help a person backtrack by providing the reverse of the forward route taken. The system operates by reference to n recorded waypoints, which have been generated from data from a GPS receiver.
U.S. Patent No. 5,528,248 to Steiner, et al., entitled "Personal Digital Location Assistant Including A Memory Cartridge, A GPS Smart Antenna And A Personal Computing Device", discloses a means for displaying a user's location as an icon on a map. The system includes a GPS Smart Antenna, a personal computing device with a display, a software operating system, and a map application program. An input select switch that is controlled by a Request To Send signal from the personal computing device enables the GPS Smart Antenna to use a single Universal Asynchronous/synchronous Receiver Transmitter (UART) chip for receiving a command/control signal from the personal computing device, and a differential GPS (DGPS) signal from a DGPS radiowave receiver.
U.S. Patent No. 5,470,233 to Fruchterman et al., entitled "System And Method For Tracking A Pedestrian", discloses a system with a software program that runs a satellite GPS designed specifically to aid blind and visually handicapped persons. The complete, preferred system comprises a GPS, a DGPS receiver, a notebook computer, a map and possibly other database(s), Sextant software, and an output system. The output system may be a voice synthesizer and/or a Braille display. The system receives a first set of coordinates from the DGPS receiver, and correlates it with a second set of coordinates in the map database. A user also can customize the system by entering preferred location and feature data into a user-defined database, including appended GPS coordinates and exclusion areas where the user desires not to enter (for example, construction zones, bodies of water, high traffic congestion areas, etc.). The system directs the user where to go at each street intersection, and can alert the user when he/she is off course (and where to go to get back on course) or approaching an exclusion area. The system can be used without GPS input as an intelligent talking map.
U.S. Patent No. 5,469,175 to Boman, entitled "System And Method For Measuring Distance Between Two Objects On A Golf Course", discloses an electronic communication system and method for accurately measuring the distance between a golf ball and the hole or pin to which the golfer desires to hit the ball. Two GPS receivers are used -- one fixed (for example, at the clubhouse) and one mobile (positioned by the golf ball). Holes/pins previously have had their coordinates determined, as has the fixed GPS receiver. Accurately measuring, in effect, the coordinates of a golf ball on a green requires that the fixed and mobile GPS receivers simultaneously measure their current positions using satellite navigational signals. Variation in the position/coordinates of the fixed receiver from the known position/coordinates thereof permits the generation of a correction signal that compensates for noise and normal fluctuations/errors in the navigational signals. The correction signal then is transmitted from the fixed GPS receiver to the mobile GPS receiver to permit determination of the true position of the golf ball, and thereby compensate for noise and fluctuations/errors in the satellite navigational signals transmitted to the mobile GPS receiver. A simple mathematical calculation then derives the distance between the golf ball and the destination hole/pin to aid the golfer in selection of the best golf club for the next shot.
U.S. Patent No. 5,389,934 to Kass, entitled "Portable Locating System", discloses a tracking system comprising a GPS unit, a data storage unit, a clock, a microprocessor, cellular telephone equipment, and a means for converting digital data to voice. The tracking system is highly portable, and can be carried by a person or a vehicle.
U.S. Patent No. 5,309,351 to McCain, et al., entitled "Communications, Information, Maintenance Diagnostic And Training System", discloses a system with portable, self-contained components for providing detailed diagnostic, repair, and maintenance information for operating equipment of various types. Hand-held control devices may be used, and communication among system elements can be by infrared signals and/or hard wiring. A satellite using an infrared frequency for communications can be used to provide a means for exchange of data between a host computer, PC's, hand-held computing units, machinery, and process controllers.
U.S. Patent No. 5,043,736 to Damell et al., entitled "Cellular Position Locating System", discloses a system for determining the position of a remote unit that receives encoded navigational GPS transmissions via an "L" band antenna and receiver. The remote unit transmits encoded data via a cellular telephone modem and transmitter to a cellular telephone system. The data then are transmitted via the cellular telephone system over telephone lines to a base computer that can decode the data and provide appropriate display thereof in map form. The remote unit can be hand-held.
The U.S. patents discussed above provide examples of data transmission to remote portable units in a variety of environments and applications. What is needed is a remote portable system that will permit the user to know in real time which satellites are "visible" or available, and/or in optimal position for any set of coordinates describing the location of the user at a particular moment in time or any selected range of time. In addition, a system is needed that will permit the user to map out, in advance, the available or optimally positioned satellites for a particular path of a mobile user, for example, while on an airplane flight.